(About the product photos...the surface was a plastic-sheet-covered table and the background was a towel. Ceiling lighting in the form of circular fluorescent tubes came from behind and in front of the subjects. Most were taken at 3.2s", f/8, and ISO 100. My Sony A200 and 75-300mm lens were used to photograph the Tamron lens while sitting on top of my tripod. Please ignore the black Sony lens cap used to balance the subjects.)

^The lens itself.

From the boxUnfortunately, the box and manual (and rear lens cap) were lost by the owner, which is my school. Those of you who followed my story ages ago will remember how I saved this lens from the spare-parts dump (since my school stopped using Minolta film cameras years ago).

So I have the lens itself, its hood, a white-coloured Minolta rear-lens cap and a Hoya UV filter on long term loan.

^Group photo. (ignore the box used to balance the rear lens cap)

Out of the box - Build qualityThe lens barrel is made of plastic of a reasonable quality. I tried gently squeezing my Sony 18-70mm and even the plastic on that seemed harder than the one on the Tamron 90mm.

The plastic material has a slight 'matt' feel to the touch.

It seems to have caught some old water stains on it which was on the internal barrel which I rarely touch though I probably left them there by accident, but it shows how fluids leave marks on the material.

What I mean by 'internal barrel' is the part of the lens that extends out when focusing at a setting other than infinity. The lens approximately doubles in length when at full 1:1 magnification.

^With the lens hood on.
From left to right: At infinity focus, at 1:2.8 magnification, at 1:1 magnification.

^Without the lens hood.
From left to right: At infinity focus, at 1:2.8 magnification, at 1:1 magnification.

As many of you probably already know, the front-most element is pretty deeply recessed which some say act as a sort-of hood by itself. This makes it really challenging to clean which is why I always leave the UV filter on - mainly because it will then be easier to clean, at the expense of some image quality.

^Autofocusing enabled to search from infinity to 1:1 and ^autofocusing limited from either 1:1 to 1:3 or 1:3 to infinity.

Now, after using this lens for over a year, I must say that I really appreciate the focusing limit switch. I rarely shoot at magnification ratios greater than 1:3 so I just keep it limited to less than that for faster focusing in my regular use. This is useful because the lens autofocuses darn slowly sometimes, hunting at both ends and pausing momentarily.

The MF (Manual Focus) ring easily beats those on my Sony 18-70mm and 75-300mm by a great tad. Now, I use L lenses (again, my school's) nearly as often as my 18-70mm, and I know what a good MF ring should feel like. The rubber ring (only as rubbery as the DT 50mm 1.8 SAM's MF ring) is comfortably damped (actually, it feels more like gears slowing its turning speed) and sufficiently sized for my small asian hands. Its pretty nice to use, but not quite nice enough for me to not mind this lens if it was MF-only.

One somewhat unique feature of this lens' MF ring is the push-pull switching between AF (autofocus) and MF. Pushing gives AF, and pulling gives MF. Loud clicks give away your focusing-mode switching, and you still have to do it again on the Sony Alpha DSLR. I have not found any problems with this system of focusing, besides the noise. Stiffness is a-OK though some will take some time to get used to it.

By the way, this lens has a metal mount. This part looks rugged

^A view of the lens from behind it.

Now, on to the hood of this lens. Its not part of the main optic (detachable) but I guess I might as well talk about it.
Its not particularly big at all. I'm sure 105mm lenses have larger & longer hoods. I guess this is a sensible design since the front element is already so deep in (and did I mention hard to clean?).

The lens hood does not have the felt-textured finish that the hoods of some L lenses have.
It is ribbed plastic (just like the inside of the lens barrel in front of the front lens element), which, to my understanding, reduces reflections.

^Side view of the lens hood.

^Another view of the lens hood.
On a side note, the weight isn't an uncomfortably-high one presumably because this is a plastic lens. I don't have a number for this, sorry.
Maybe 400g at a rough estimate.

Optical qualitiesA few websites that I've found online have praised this lens and the DI version for their optical quality. Let's have a look at this lens' results.

We'll start off with the distortion test.

There is negligible (seemingly-barrel) distortion. Nothing significant to report in this category.

Moving on to the CA (Chromatic Aberration) test.

This is the scene that I have used to test for CA. The subject is a reflective metal can with painted text.

^This was shot at f/8 and has no purple colour fringing that is detectable by my eyes.

These are the test results:
^From left to right: f/2.8 , f/4, f/5.6
(All three are clickable to larger-sized versions of the crops)

This lens controls CA very well! There is very little purple-coloured fringing even at f/2.8. Don't be misled by the shots taken with this lens that are on my flickr - those had the use of the Hoya UV filter which reduced the image quality dramatically (but I still use it for protection).
At f/4, purple coloured fringing has been reduced even further but small traces are still visible.
Virtually all CA has disappeared by f/5.6 and the text are completely white, just like at f/8.
***
Now...for the test that matters the most to many photographers.. Lens sharpness!

As usual, I'll first show you the scene used for the tests.
I shot these through a window grille, so some parts of the source photo are obscured because I did not want to stick the lens out of my window in the sea of apartment flats. Its not a good thing to be seen with a camera jutting out of an apartment window. Nothing to worry about - nobody accused of me of any misdemeanour and the test was not affected.

^This is the scene used for the centre sharpness test.

Both tests were conducted within minutes of each other and were of the same subject taken with identical metering, exposure and autofocusing settings.

^This is the scene used for the corner sharpness test.

Ok, we'll now start with the corner sharpness test results.
^1st row, from left to right: f/2.8, f/4, f/5.6, f/8
^2nd row, from left to right: f/11, f/16, f/22, f/32
(all thumbnails are clickable to large 100+% crops)
(I have only posted a further-cropped thumbnail of the 100% crops for illustration purposes - you should click the links to actually compare the sharpness differences)

The corner sharpness results are lovely! Obviously far better (even wide open) than my 18-70 which I tested haphazardly a while back.
The wide-open results already show high sharpness, albeit with purple fringing. The f/5.6 and f8 aperture values seem to be winners here, with negligible differences in sharpness. They both produce the highest possible sharpness achievable in the image-corner by this lens.
Diffraction limiting sets in by f/11, and the aperture values larger than that (i.e. smaller aperture size) produce even softer images than at f/2.8.
/
If you were pleasantly surprised by the corner sharpness results, you will be wow-ed by the lovely centre sharpness results. They make me want to put all my subjects in the centre - just kidding, the corners are pretty good too.

^1st row, from left to right: f/2.8, f/4, f/5.6, f/8
^2nd row, from left to right f/11, f/16, f/22, f/32
(all thumbnails are clickable to large 100% crops)
(I have only posted a further-cropped thumbnail of the 100% crops for illustration purposes - you should click the links to actually compare the sharpness differences)

The centre sharpness results are 'proportional to' and reflective of the corner sharpness results. All of the aperture values retain their 'rank' of sharpness, and are proportionally sharper than their corner counterparts.
-
All in all...great lens results!

[NOTE-temporary: I have had some issues trying to conduct the vignetting and flare/ghosting tests, so please be patient while I'm trying to get a solution!]

SnS

Last edited by SCREAMnSHOUT on Sun Sep 27, 2009 2:13 pm, edited 18 times in total.